Transgenic proteoid roots of white lupin: a vehicle for characterizing and silencing root genes involved in adaptation to P stress
Article first published online: 9 NOV 2005
The Plant Journal
Volume 44, Issue 5, pages 840–853, December 2005
How to Cite
Uhde-Stone, C., Liu, J., Zinn, K. E., Allan, D. L. and Vance, C. P. (2005), Transgenic proteoid roots of white lupin: a vehicle for characterizing and silencing root genes involved in adaptation to P stress. The Plant Journal, 44: 840–853. doi: 10.1111/j.1365-313X.2005.02573.x
- Issue published online: 9 NOV 2005
- Article first published online: 9 NOV 2005
- Received 22 May 2005; revised 20 August 2005; accepted 6 September 2005.
- Agrobacterium rhizogenes;
- cluster roots;
- multidrug and toxin efflux (MATE);
- phosphorus deficiency;
- proteoid roots;
- white lupin
White lupin (Lupinus albus L.) has become an illuminating model for the study of plant adaptation to phosphorus (P) deficiency. It adapts to −P stress with a highly coordinated modification of root development and biochemistry resulting in short, densely clustered secondary roots called proteoid (or cluster) roots. In order to characterize genes involved in proteoid root formation and function in a homologous system, we have developed an Agrobacterium rhizogenes-based transformation system for white lupin roots that allows rapid analysis of reporter genes as well as RNA interference (RNAi)-based gene silencing. We used this system to characterize a lupin multidrug and toxin efflux (Lupinus albus MULTIDRUG AND TOXIN EFFLUX, LaMATE) gene previously shown to have enhanced expression under −P stress. Here, we show that LaMATE had high expression in proteoid roots not only under −P, but also under −Fe, −N, −Mn and +Al stress. A portion containing the putative LaMATE promoter was fused to GUS and enhanced green fluorescence protein (EGFP) reporter genes, and a translational LaMATE::EGFP fusion was constructed under control of the LaMATE promoter. The LaMATE promoter directed P-dependent GUS and EGFP expression to proteoid roots. Confocal microscopy in white lupin and Arabidopsis point to the plasma membrane as the likely location of the LaMATE protein. LaMATE displayed homology to FRD3 in Arabidopsis, but did not complement an Arabidopsis ferric reductase defective 3 (FRD3) mutant. RNAi-based gene silencing was shown to effectively reduce LaMATE expression in transformed white lupin roots. LaMATE RNAi-silenced plants displayed an about 20% reduction in dry weight.